Patent Application
20140263825
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The rotor system of an aircraft, such as a helicopter or tiltrotor aircraft, may act as a source of vibration during operation of the aircraft. The aircraft may include a vibration isolation or suppression system to attenuate the vibration as it is transmitted from the rotor system to the airframe. Isolating the vibration as it is transmitted to the airframe may serve to mitigate material fatigue, flight control problems, or other issues that may arise from excessive levels of vibration within the airframe. The amount of attenuation or isolation provided by a passive vibration isolation system may be reduced when acted upon by a vibration of a frequency outside of a designed or tuned frequency range of the passive isolation system.
In some embodiments of the disclosure, an apparatus is disclosed as comprising an active vibration isolation system that comprises a vibration isolator, a dual fluid pump in fluid communication with the vibration isolator and a hydraulic system, wherein the dual fluid pump is configured to segregate a tuning fluid from a hydraulic fluid and an electric-hydraulic servo valve in fluid communication with the dual fluid pump.
In other embodiments of the disclosure, an active vibration control system for an aircraft is disclosed as comprising a vibration isolator, a dual fluid pump in fluid communication with both the pylon mount and a hydraulic system of the aircraft, wherein the dual fluid pump is configured to segregate a tuning fluid from a hydraulic fluid and a control computer configured to measure vibration within a fuselage of the rotorcraft and be in signal communication with the vibration isolator and the dual fluid pump.
In still other embodiments of the disclosure, a method of isolating vibration is disclosed as comprising isolating vibration transmitted from a gearbox using a vibration isolation system, outputting a control signal to an electric-hydraulic servo valve, communicating a first fluid between the electric-hydraulic servo valve and a dual fluid pump, communicating a feedback signal to the control computer corresponding to the measured displacement of a piston within the pump using a displacement transducer and communicating a second fluid between the vibration isolation system and the dual fluid pump, wherein the first fluid is segregated from the second fluid via the dual fluid pump.
For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description:
It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed systems and/or methods may be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.
In some cases, it may be desirable to provide an AVIS configured to attenuate vibrations generated by the rotor system of an aircraft, such as a helicopter or other rotorcraft. In some embodiments of the disclosure, the AVIS may provide more effective isolation of vibrations across a larger frequency range relative to the isolation provided by passive vibration isolation systems. In some embodiments, the AVIS may comprise an EHSVAP and a dual fluid pump in fluid communication with a liquid inertia vibration eliminator (LIVE™) and the hydraulic system of the aircraft. In some embodiments, a control computer of the AVIS may provide feedback to the dual-fluid piston pump via signal outputs from a displacement transducer and one or more vibration sensors coupled to the aircraft. In some embodiments, the dual-fluid piston pump may be configured to actuate the LIVE using feedback from the control computer.
Referring now to
The AVIS 100 may be configured to act as a buffer to attenuate or isolate vibratory forces transmitted to the isolated mass 30 of the system 10. In an embodiment, AVIS 100 generally comprises a vibration isolation system 110, an EHSVAP 130, a control computer 170 and at least one vibration sensor 180. In some embodiments, EHSVAP generally comprises a servo valve 134 actuated by an electromechanical member 132, a dual fluid pump 140 and a displacement transducer 150. In this embodiment, vibration isolation system 110 is coupled between the vibratory mass 20 and the isolated mass 30 of the system 10, allowing vibration isolation system 110 to attenuate vibratory forces produced by vibratory mass 20 before they are transmitted to the isolated mass 30.
In an embodiment, vibration isolation system 110 may comprise a vibration isolator, such as a LIVE unit. LIVE unit vibration isolators are disclosed in U.S. Pat. No. 4,236,607, which is incorporated in its entirety herein by reference. In this embodiment, the LIVE unit may comprise a piston coupled to the vibratory mass 20 and disposed within a housing coupled to the isolated mass 30 that is filled with a tuning mass comprising a tuning fluid having a relatively high density and low viscosity. In an embodiment, the tuning fluid has a density of about 1.6-1.9 grams per centimeters cubed, a kinematic viscosity of about 0.4-0.9 centistokes, a boiling point of about 80-120° Celsius and a pour point of lower than about −40° Celsius. A tuning port may extend axially through the piston, providing fluid communication between opposing fluid chambers disposed between the housing and each axial end of the piston Vibratory or oscillatory motion from mass 20 may be transmitted to the piston, causing the tuning fluid disposed within the housing to flow between each fluid chamber via the tuning port.
The effectiveness of the LIVE unit's ability to isolate vibration (i.e., prevent vibration from being transmitted from vibratory mass 20 to isolated mass 30) at a given amplitude and frequency may depend on the total mass of the tuning fluid, the cross-sectional area of the tuning port, the cross-sectional area of the piston, the stiffness of the piston motion and other factors. Further, the effectiveness of the LIVE unit in isolating vibration varies with the frequency of vibration of the vibratory mass 20. Thus, a LIVE unit may more effectively isolate vibration within a particular vibration frequency range than vibration at frequencies outside of the range.
One factor in the relationship between the effectiveness of vibratory isolation of the LIVE unit and vibration frequency may relate to the passive nature of the LIVE unit, in that flow of the tuning fluid through the tuning port and oscillation of the piston is driven passively in response to vibration of the vibratory mass 20. In some embodiments, AVIS 100 may allow for active pumping of tuning fluid through the vibration isolation system in response to a signal from a controller, such as control computer 170. In this manner, the vibration isolation provided by system 110 may be continuously adjusted during operation of the system 10. For example, vibration isolation system 110 may be adjusted or actuated in response to the frequency and/or amplitude of the vibration transmitted to system 110 by vibratory mass 20. Also, system 110 may be adjusted in response to the measured vibration within isolated mass 30, as a result of vibrations being transmitted from isolation system 110 to isolated mass 30.
In an embodiment, EHSVAP 130 is configured to actuate the vibration isolation system 110 in response to signals or data received from a controller, such as control computer 170. In actuating the vibration isolation system 110 in response to signals from control computer 170, EHSVAP may be configured to convert the electronic signals from control compute 170 into a hydraulic force for actuating vibration isolation system 110 via the hydraulic power supplied by the hydraulic system 40.
In an embodiment, the electromechanical member 132 of ESHVAP 130 may be configured to convert a received signal from the control computer 170 into a mechanical force for actuating the servo valve 134. The servo valve 134 may be in fluid communication with the hydraulic system 40 and the dual fluid pump 140. In an embodiment, servo valve 134 may comprise a hydraulic spool or servo valve having a plurality of ports and a piston that is translatable in response to actuation from the electromechanical member 132. Translation of the piston may result in fluid flow through one or more of the ports, where each port is in fluid communication with a corresponding port of the dual fluid pump 140.
In some embodiments, the dual fluid pump 140 may be configured to displace tuning fluid of the isolation system 110 in response to actuation from servo valve 134. Pump 140 may comprise a piston that is translatable in response to the displacement of hydraulic fluid from hydraulic system 40 via actuation of servo valve 134. The piston may displace tuning fluid in response to translation while allowing for the segregation of the tuning fluid and the hydraulic fluid provided by the hydraulic system 140. In some embodiments, the displacement transducer 150 may be configured to output a piston position signal corresponding to an axial position of the piston. In an embodiment, displacement transducer 150 may be a linear variable differential transformer (LVDT).
In some embodiments, the actuation of dual fluid pump 140 may actively alter the flow of tuning fluid through the tuning port of the vibration isolation system 110. The active actuation of dual fluid pump 140 may produce oscillating or sinusoidal flow of tuning fluid through the isolation system 110, which may isolate or attenuate vibration transmitted from the vibratory mass 20. For instance, the piston of pump 140 may be axially displaced in an oscillatory manner, resulting in oscillator or sinusoidal flow of tuning fluid through system 110. In an embodiment, pump 140 may be configured to allow for the adjusting the magnitude of tuning fluid displaced, the sinusoidal frequency of the displaced tuning fluid and the phase angle of the displaced tuning fluid.
In some embodiments, one or more vibration sensors 180 may be configured to measure vibrations within isolated mass 30. For example, one or more sensors 180 may be coupled to the isolated mass 30. In an embodiment, a plurality of sensors 180 may be coupled to isolated mass 30 at various locations of the mass 30. Sensors 180 may comprise accelerometers configured to provide a signal output corresponding to the proper acceleration of the sensor 180 in the fore-aft, lateral and vertical directions. However, in other embodiments sensors 180 may comprise other types of sensors capable of measuring vibration of a body or mass, such as velocity sensors, proximity sensors, piezoelectric sensors and the like.
In some embodiments, the control computer 170 is configured to receive signals outputted from the displacement transducer 150 and sensors 180 and output a command signal to the electromechanical member 132 for actuating servo valve 134. Control computer 170 may comprise a controller algorithm for processing the signal inputs provided by transducer 150 and sensors 180 to form a signal output configured to minimize the magnitude of vibratory force transferred between the vibratory mass 20 and the isolated mass 30. For instance, in an embodiment, computer 170 may comprise a control loop feedback mechanism such as a proportional-integral-derivative (PID) controller algorithm. In some embodiments, control computer 170 may also comprise one or more amplifiers or other components configured for conditioning the signals outputted by transducer 150 and sensors 180.
Referring now to
The method 190 may continue at block 198 by providing a command signal using a control computer, such as control computer 170. The method 190 may continue at block 200 by actuating a servo valve, such as servo valve 134, in response to the command signal outputted by the control computer. In some embodiments, actuating the servo valve may comprise actuating the valve using an electromechanical member configured to apply a mechanical force on the servo valve. The method 190 may continue at block 202 by actuating a dual fluid pump in response to actuation provided at block 200. In some embodiments, actuating a dual fluid pump may comprise using hydraulic pressure and energy provided by a hydraulic system. In an embodiment, the hydraulic system may be a component of the isolated mass, such as isolated mass 30.
The method 190 continues at block 204 by actuating the vibration isolator described in block 194 in response to the actuation provided at block 202. In some embodiments, actuating the vibration isolator may comprise displacing a tuning fluid between the vibration isolator and the dual fluid pump. In an embodiment, the tuning fluid has a density of about 1.6-1.9 grams per centimeters cubed, a kinematic viscosity of about 0.4-0.9 centistokes, a boiling point of about 80-120° Celsius and a pour point of lower than about −40° Celsius. The method 190 may continue at block 206 by providing a displacement measurement of a piston of the dual fluid pump to the control computer described at blocks 198 and 200. In some embodiments, providing a displacement measurement may comprise outputting a signal from a LVDT corresponding to the displacement measurement. Further, referring back to block 198, providing a control signal may comprise processing the measured vibration signal at block 196 and the displacement signal provided at block 206.
Referring now to
The rotor system 330 of drive train 320 may produce sinusoidal or oscillatory vibratory forces during operation, the frequency range and amplitude of which may depend upon the number of rotor blades, the revolutions per minute (RPM) of the rotor, the speed of the aircraft and other factors. The frequency range of vibratory forces generated by the drive train 320 may also depend upon whether the rotorcraft system is a variable rotor speed (RPM) rotorcraft having a rotor with a plurality of operational rotor speeds. In an embodiment, rotor system 330 of drive train 320 may be of the variable rotor speed type. However, in other embodiments rotor system 330 may only have a single operational rotor speed.
System 300 further includes an AVIS 340 that is an embodiment of the AVIS 100 disclosed in
Referring now to
Referring now to
In this embodiment, EHSV 370 generally comprises an electromechanical member 372 and a servo valve 380. In some embodiments, member 372 generally comprises an electro-magnetic torque motor having a plurality of coil windings 374 in signal communication with the control computer 420. Each winding 374 is disposed about a magnet 376 coupled to an elongate arm 378. Member 372 may further comprise an amplifier for conditioning signals communicated by the control computer 420. In this embodiment, servo valve 380 generally comprises a fluid conduit 382 having a first pair of supply ports 384a, 384b, a second pair of supply ports 386a, 386b, a pair of return ports 388a, 388b and a pair of outlet ports 390a, 390b, all in fluid communication with the hydraulic system 314 of rotorcraft 310 shown in
In this embodiment, valve 380 further comprises a piston 392 disposed within conduit 382. Piston 392 has a first end 392a, a second end 392b and comprises a first pair of annular seals 394a, 394b, and a second pair of annular seals 396a, 396b. Piston 392 also includes an axial throughbore 392c that allows for fluid communication between the pair of supply ports 384a, 384b. Elongate arm 378 physically engages piston 392 between seals 394b and 396a, and may axially displace piston 392 within conduit 382 in response to a force applied to the arm 378 from magnet 376 and windings 374. As piston 392 is axially displaced within conduit 382, supply port 386a may be sealed by annular seal 394a, return port 388a may be sealed by annular seal 394b, supply port 386b may be sealed by annular seal 396b and return port 388b may be sealed by annular seal 396a.
As shown in
In some embodiments, dual fluid pump 400 is configured to allow for the communication of tuning fluid between LIVE unit 354 and pump 400 and hydraulic fluid between servo valve 380 and pump 400 while maintaining segregation between the tuning fluid and hydraulic fluid. Dual fluid pump generally comprises a housing 402 having a piston assembly 404 disposed in a passage 406 therein. Piston assembly 404 has a first end 404a, a second end 404b and a flange 405 axially disposed between the first and second ends 404a and 404b. In this embodiment, three fluid chambers are formed within the housing 402: a first outer chamber 408 disposed between an inner surface of passage 406 and first end 404a of piston assembly 404, a second outer chamber 410 disposed between an inner surface of passage 406 and the second end 404b of piston assembly 404, and a third or inner chamber 412 that is formed between a pair of annular seals 409, disposed radially between the housing 402 and an outer surface of the piston assembly 404. Also, an annular seal 409 is disposed radially between an outer surface of piston assembly 404 and an inner surface of passage 406 near each end 404a, 404b, of piston assembly 404.
In this embodiment, an annular seal 411 is created between an outer radial surface 405a of flange 405 and the inner surface of the passage 406 of housing 402. Seal 411 may divide third chamber 412 into a first portion 412a and a second portion 412b. Housing 402 of dual fluid pump 400 may further comprise a plurality of ports for providing fluid communication between pump 400 and both LIVE unit 354 and servo valve 380. In this embodiment, housing 402 further comprises a pair of tuning fluid ports 414a, 414b. First tuning port 414a of housing 402 is in fluid communication with first fluid conduit 368a and corresponding first port 366a of LIVE unit 354. Second tuning port 414b is in fluid communication with second fluid conduit 368b and second port 366b of LIVE unit 354.
In this embodiment, housing 402 of dual fluid pump 400 may comprise a pair of vent cavities 413a and 413b, with cavity 413a disposed axially between first end 404a and third chamber 412 and cavity 413b disposed axially between third chamber 412 and second end 404b of piston assembly 404. Vent cavities 413a and 413b may be configured to allow for the venting to atmosphere of the hydraulic fluid 387 or the tuning fluid 357 in the event that any of the annular seals fail during operation, and thus form a leak path to one of the vent cavities 413a and 413b.
In this embodiment, housing 402 further comprises a pair of hydraulic fluid ports 416a, 416b. First hydraulic fluid port 416a is in fluid communication with first conduit 398a and corresponding first outlet port 390a of valve 380. Second hydraulic port 416b is in fluid communication with second conduit 398b and corresponding second outlet port 390b of valve 380.
In an embodiment, EHSVAP is configured to adjust the oscillating or sinusoidal flow of tuning fluid through the LIVE unit 354. In this embodiment, a control signal outputted from the control computer 420 may be received by the electromechanical member 372, which may cause elongate arm 378 to actuate sinusoidally. Physical engagement between arm 378 and piston 392 may transmit the sinusoidal movement of arm 378 to piston 392. As piston 392 is displaced sinusoidally in conduit 382, hydraulic fluid is displaced to and from dual fluid pump 400 in an oscillating pattern. For example, as piston 392 is displaced axially in a first direction towards first end 392a, hydraulic fluid is displaced from the hydraulic system 314 into the first chamber 408 of dual fluid pump 400 via first fluid conduit 398a, and hydraulic fluid is displaced from the second chamber 410 of pump 400 back into system 314 via second fluid conduit 398b. Once piston 392 has reversed direction, and is displaced in the direction of second end 392b (as shown in
In an embodiment, the oscillating flow of hydraulic fluid between servo valve 380 and dual fluid pump 400 results in a corresponding oscillating or sinusoidal movement of piston assembly 404 within passage 406. For instance, when piston 392 of valve 380 is disposed in the arrangement shown in
In an embodiment, the sinusoidal displacement of piston assembly 404 in passage 406 results in an adjustment of the oscillating flow of tuning fluid into and out of chambers 362a, 362b, tuning port 358, of LIVE unit 354 resulting from vibratory forces passing through the unit 354. Specifically, a closed fluid system 418 having an approximately constant or fixed volume is formed by the combination of first and second chambers 362a, 362b, tuning port 358, first and second fluid conduits 368a, 368b, and the third chamber 412 of dual fluid pump 400. As piston assembly 404 is displaced sinusoidally within passage 406, the relative size of first portion 412a and second portion 412b shift, causing tuning fluid to be displaced within fluid conduits 368a, 368b and tuning port 358. For instance, as piston assembly 404 is displaced axially in the direction of first end 404a, the relative volume of first portion 412a is decreased, thus expelling or pumping fluid from first portion 412a through conduit 368a and into first chamber 362a. In order to equalize fluid pressure within fluid system 418, tuning fluid within first chamber 362a is displaced through tuning port 358 toward second chamber 368b. Tuning fluid within second chamber 362b may be displaced through conduit 368b toward second portion 412b of chamber 412. The flow of tuning fluid within closed system 418 may be reversed by reversing the axial direction of displacement of piston assembly 404 within 406, towards second end 404b.
In some embodiments, the axial position or displacement of piston assembly 404 may be continuously monitored and an output signal corresponding to the axial position of piston assembly 404 may be transmitted via the displacement transducer 424, which may be coupled to the pump 400. The signal output of displacement transducer 424 may be used to compute the sinusoidal frequency of piston assembly 404 using control computer 420. In some embodiments, control computer 420 may be configured to adjust the sinusoidal frequency of piston assembly 404 in response to the frequency of vibrations measured by the one or more vibration sensors 422 coupled to the fuselage 312. In an embodiment, the control computer 420 and EHSV 370 may be configured to adjust the volume of tuning fluid displaced within closed system 418, the sinusoidal frequency of the displaced tuning fluid and the phase angle of the displaced tuning fluid relative to the azimuth position of the rotor 334 of rotor system 330. In an embodiment, a control algorithm, such as a PID controller algorithm may be used to compute an output signal in response to the signals outputted from sensors 422 and displacement transducer 424. In an embodiment, displacement transducer 424 may comprise an LVDT.
Referring now to
Also, housing 462 includes a flange 470 that extends into passage 464 and sealingly engages an outer surface of piston assembly 466. This arrangement forms four fluid chambers: a first fluid chamber 472a disposed between flange 470 of housing 462 and second flange 468b of piston assembly 466, a second fluid chamber 472b disposed between flange 470 and fourth flange 468d of piston assembly 466, a third fluid chamber 472c disposed at first end 466a of piston assembly 466 and a fourth fluid chamber 472d disposed at second end 466b of piston assembly 466. Housing 462 further comprises a plurality of ports, with a first pair of inlet ports 474a, 474b, providing fluid communication from the servo valve 380 to first and second fluid chambers 472a, 472b, respectfully, and a pair of outlet ports 476a, 476b, providing fluid communication between third and fourth fluid chambers 472c, 472d, and LIVE unit 354. Displacement transducer 424 may measure the position or displacement of piston assembly 466 in passage 464.
Referring now to
Referring now to
At least one embodiment is disclosed and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, Rl, and an upper limit, Ru, is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=Rl+k*(Ru−Rl), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Unless otherwise stated, the term “about” shall mean plus or minus 10 percent. Of the subsequent value. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of the term “optionally” with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention.
